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Reaction Lab
Tap, click, or press space to start.
Wait for green, then tap fast.

Wait for the panel to turn green, then tap the instant it does. Jump early and the round restarts. Clear five rounds and your average reaction time is ranked against global tiers.

🔴
Red means hold. Tapping now restarts the round.
🟢
Green means go. Tap as fast as you can.
📊
Five rounds, averaged and ranked against global tiers.

FAQ

How does Reaction Lab work?
The panel starts red, then flips to green after a random wait. The instant it turns green, tap. The game clocks the milliseconds between the switch and your tap, and repeats it for five rounds.
What happens if I tap too early?
Tapping while the panel is still red is a false start, and that round simply restarts, with no time recorded. The trick is staying loose so you can fire the instant green hits, without jumping the gun.
What counts as a good reaction time?
Most people land between 200 and 300 milliseconds. Your average across the five rounds drops you into a tier, from Sleepy up to Cheetah, and your fastest single tap is saved as your best to chase.
Is Reaction Lab free, and do I need an app?
Reaction Lab is completely free with no app to download and no signup. It runs in any modern browser on Android or desktop, works offline once loaded, and saves your best time locally on your own device.
Reaction Lab is a five-round reflex benchmark: wait for the screen to flash green, then tap the instant it does. It's the classic red-light, green-light test for raw reaction time, scored as your millisecond average across the run. One go takes under a minute and hands you a real number to beat, which is what makes it so easy to replay on Android or desktop. Reaction Lab is completely free, needs no app and no signup, works offline, and keeps your best time private on your own device.

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